The present invention relates to systems, devices, and methods for a wind turbine with variable diameter blades whose diameter is controlled by arm length and/or angle.
This addresses the problem of how a turbine can make use of low wind speeds but survive in high wind speeds, or even just how to survive in high wind speeds alone. It shows how to achieve various efficiencies based on the configuration of the blades combined with a parameter called the Tip Speed Ratio (TSR). This requires coordination of the parameters of a turbine in order to achieve the proper shape and control configuration for a particular speed. An example of an application is the environment of parts of India, where the wind speeds are low most of the year and high at other times during monsoon season, or in other hurricane areas of the world.
Here is an examination of some potential prior art:
Dawson (US 2010/0158687) is not relevant because it applies to rotor blades and involves changing the length of the blades. That is different from the current application, which does not discuss changing the blade shape but does discuss changing the turbine diameter. It is also specific for a horizontal axis turbine.
Potter (U.S. Pat. No. 4,342,539) has a concept of decreasing the width of the wind machine but proposes a totally unrelated concept of telescoping numerous airfoils. Our application is different in that it does not use telescoping and in some embodiments uses non-airfoil blades. Potter depends on sails and furling, whereas we use solid blades. Potter's tower is capable of tilting, whereas ours is ideally rigid. His sails lower into storage mode, whereas the current application involves retraction.
Hulls (U.S. Pat. No. 5,531,567) applies to tensioning Darrieus type blades and is not relevant.
Quraeshi (U.S. Pat. No. 6,394,745) uses a pitch control on lift vertical axis blades. It does not alter the distance of the blade center from the shaft.
Jamieson (U.S. Pat. No. 6,972,498) extends the outer diameter through various means, whereas the current application works by adjusting either the internal diameter or the angle.
In summary, there is no prior art known to the authors of this application that addresses the mechanics and aerodynamics of the current invention.